This invention relates to the field of brake bleeder valves used to bleed hydraulic fluid lines of hydraulic brake systems of vehicles, and particularly to those having some kind of check valve mechanism within the bleeder valve body or combined therewith.
Brake bleeder valves of this kind which are presently known have the disadvantage that the passageway through the valve body in which the check valve mechanism is located opens directly into the hydraulic cylinder or chamber of the system located at each wheel. If the check valve leaks, hydraulic fluid can flow directly from the system out through the bleeder valve. Some attempts to correct this problem have provided such things as a two piece bleeder valve, in which one piece is a cap that can be tightened and loosened relative to the other piece that is screwed into the housing of the hydraulic cylinder or chamber. The one piece which is screwed into the housing has a first hemi-spherical valve seat to receive the bottom half of a ball check valve, and the cap has a second hemi-spherical valve seat to receive the top hand of the ball check valve. When the cap is screwed down tight on the other piece, the ball check valve is thereby held in the valve seat in the valve closed position. In the event a stripped thread or obstruction of some kind prevents the cap from being fully and completely tightened, the ball check valve remains loose with only a spring biasing it toward the valve closed position. When the brakes of the vehicle are applied thereby pressurizing the hydraulic fluid in the lines, such pressurized fluid enters the passageway of this prior art type of bleeder valve which opens directly into the system. The pressurized fluid can become strong enough to overcome the bias of the spring holding the check valve in place, whereby fluid can leak out through the bleeder valve.
The present invention overcomes this and other problems of prior art brake bleeder check valves. The valve body in accordance with the present invention is a one-piece unit in which the entrance to the passageway through the valve body is in the side wall of the valve body and is not in communication at all with the hydraulic cylinder or chamber of the hydraulic system when the bleeder valve body is in its tightened and closed position. In this type of bleeder valve body construction, no separate mechanism is needed to hold the check valve in place since pressurized hydraulic fluid cannot reach the check valve and force it open until the one-piece valve body itself has been loosened enough to permit hydraulic fluid to flow out of the closed system into the bleeder valve recess whereby it can then enter the side wall entrance of the bleeder valve body.
Examples of prior art bleeder valves known to the inventor in this case include those disclosed in the following United States Patents.
U.S. Pat. No. 4,524,800 discloses a two part brake bleeder check valve of the prior art type described above.
U.S. Pat. No. 2,865,398 discloses a brake bleeder check valve assembly that is not a permanent part of the hydraulic system, but has to be either inserted in place of the original screw plug or connected to an original equipment air bleed connector by means of an adapter.
U.S. Pat. No. 2,256,516 discloses a bleeder fitting for brake cylinders which is also not a permanent part of the hydraulic brake system. The original plug has to be removed and the bleeder fitting disclosed in this patent is then screwed in place. It has a direct opening to the hydraulic system whereby pressure on the fluid in the system will be applied directly to the check valve thereby forcing it open. This type of bleeder fitting could not be used as a permanently mounted bleeder check valve of a hydraulic brake system.